"Researchers have discovered a timing attack on RSA keys, to which
OpenSSL is generally vulnerable, unless RSA blinding has been turned
on.

Typically, it will not have been, because it is not easily possible to
do so when using OpenSSL to provide SSL or TLS.

The enclosed patch switches blinding on by default. Applications that
wish to can remove the blinding with RSA_blinding_off(), but this is
not generally advised. It is also possible to disable it completely by
defining OPENSSL_NO_FORCE_RSA_BLINDING at compile-time.

The performance impact of blinding appears to be small (a few
percent)."